Heretofore, load-carrying conveyor chains used by circulating through curved paths are known.
For example in Japanese Patent No. 3580415, there has been known a so-called horizontal driving chain 300 in which top plates 380 are attached in parallel to outer and inner link plates 320 and 310 as shown in FIGS. 13 and 14. FIG. 14 is an inverted plan view of the chain when the chain in FIG. 13 is seen from the direction of an arrow XIV. The horizontal driving chain 300, whose top plates 380 are molded from engineering plastics, is often used as a carrying conveyor chain in sushi-go-round restaurants.
There has been also known in Japanese Patent No. 3398110 a top chain 400 in which front and back portions of each top plate 480 are formed into comb-like concave and convex shapes as shown in FIG. 15, which is an inverted plan view of the top chain 400. A bush hole 460 in a rear portion of each link 440 of the top chain 400 is enlarged so as to be wide-opened in an axial direction so that the chain can be used even in a curved track of the conveying path. The contiguous links 440 are allowed to be angled to each other in the horizontal direction when pins 420 are inserted into the pin holes 450 and the bush holes 460 by aligning pin holes 450 in the front portion of the one link with bush holes 460 in the rear portion of the contiguous link.
However, the horizontal driving chain 300 as described above has a problem that because it cannot bend in the vertical direction with respect to the top plates 380, i.e., it cannot be bent backward, from its structure, it is unsuitable for carrying objects horizontally elongated a conveying path having three-dimensional spatial bends in the vertical direction on its way.
Meanwhile, the top chain 400 as described above has a problem that because an orbit where the teeth of a sprocket engage in receptacles in the bush-corresponding portion of each link 440 below the top plate 480, i.e., a pitch circle of the sprocket SP, is considerably closer to the center of rotation of the sprocket from the center of rotation than the pitch circle of the chain CC (when seen above), hooking of teeth of the sprocket is shallow and the teeth tend to jump.